JPH038469B2 - - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates to refrigeration systems and, more particularly, to purge systems for removing noncondensable gases and other contaminants from refrigeration systems.

Within a refrigeration system, various non-condensable gases and other contaminants typically mix with the refrigerant used in the refrigeration system and end up at some point in the refrigeration system, such as the top of the condenser in a vapor compression refrigeration system. They tend to gather together. The presence of non-condensable gases and other contaminants in a refrigeration system reduces the efficiency of the refrigeration system. This is because, for example, their presence requires high condenser pressures, which reduces the cost of electricity or the amount of cooling fluid, such as relatively cold water, used to condense the refrigerant in the condenser. This is because it involves an increase. The capacity of the refrigeration system is also reduced as the non-condensable gas displaces the refrigerant vapor flowing through the refrigeration system. To overcome the above-mentioned drawbacks, various types of purge devices are used to remove or purge noncondensable gases and other contaminants from refrigeration systems. Such purge devices typically include a purge chamber for collecting non-condensable gases such as air and purging them to the atmosphere. The gas that collects in this purge chamber also contains water vapor and some refrigerant vapor. Typically, a heat transfer coil is located within the purge chamber and is supplied with a cooling fluid, such as water or a refrigerant. This heat transfer coil operates as a condensing coil that condenses refrigerant and water vapor in the purge chamber. These condensed liquid compositions, such as refrigerant and water, are then removed from the purge chamber. Typically, the condensed liquid refrigerant is circulated through the refrigeration system and the condensed water is purged from the refrigeration system. Noncondensable gases are typically vented to the atmosphere by automatic pumps that operate in response to the pressure difference between the purge chamber and the condensability of the refrigeration system.

In purge systems of the type described above, a purge safety switch is used to sense the pressure difference between the refrigerant in the evaporator and the refrigerant in the condenser of the refrigeration system. The purge safety switch opens when it detects that the refrigerant pressure difference between the evaporator and condenser has fallen below a certain value at which it is undesirable to operate the purge system. Prevents purge system operation. In this way, the purge safety switch will prevent the purge system from operating during periods where it is not beneficial to operate the purge system, such as during intervals when the refrigeration system is shut down and the refrigerant pressure in the evaporator is approximately equal to the refrigerant pressure in the condenser. Interfering with the operation of the purge system for a period of time.

Differential pressure switches used as purge safety switches in the manner described above are suitable for use with, and have worked satisfactorily with, many purge control systems used in refrigeration systems. However, these differential pressure switches have certain inherent disadvantages. For example, these differential pressure switches are not ideally suited for use with electronic control systems because they require a converter to convert the pressure signal to an electrical signal compatible with the electronic control system.
Additionally, these differential pressure switches are mechanical devices that are inherently subject to mechanical wear and tear, are prone to mechanical failure, and are relatively costly.

SUMMARY OF THE INVENTION Accordingly, one object of the present invention is to provide a refrigeration system with a purge system having a purge safety switch that can be adapted to an electronic control system for the refrigeration system.

Another object of the present invention is to reduce the cost and improve the reliability of purge systems used to remove noncondensable gases and other contaminants from refrigeration systems.

Yet another object of the invention is to electronically detect operating conditions in a refrigeration system in which it is undesirable to operate a purge system, such that there is no need to convert mechanical signals into electrical signals. It is to provide an electrical signal indicating the operating status directly to the control system for the purge system.

These and other objects of the invention provide a method and control system for a refrigeration system in which an electronic temperature sensor is used in conjunction with an electronic controller to provide the functionality of a purge safety switch without the use of a differential pressure switch. achieved by.
According to the invention, a first temperature sensor is placed in the evaporator of the refrigeration system and provides a first electrical signal indicative of the temperature of the refrigerant in the evaporator. A second temperature sensor is located in the condenser of the refrigeration system and provides a second electrical signal indicative of the temperature of the refrigerant within the condenser.
The first electrical signal and the second electrical signal are monitored by an electronic controller, such as a microcomputer control system, which controls the first electrical signal and the second electrical signal according to a programmed procedure. The signal is processed to determine a temperature difference between the evaporator refrigerant and the condenser refrigerant. The electronic controller generates a control signal when a temperature difference of the refrigerant monitored by the electronic controller is less than a preselected value indicating that operating the purge system is undesirable. . Switch means electronically connected to the electronic control unit inhibits operation of the purge system in response to generation of a control signal by the electronic control unit.

Other objects and advantages of the invention will become apparent from the following detailed description of the invention, taken in conjunction with the accompanying drawings. It should be noted that like reference numerals indicate similar elements in the drawings.

DESCRIPTION OF THE EMBODIMENTS Referring to FIG. 1, a schematic diagram of a refrigeration system having a purge system operated in accordance with the principles of the present invention is shown. The refrigeration system shown in FIG. 1 is a typical vapor compression refrigeration system in which the refrigerant is compressed by a compressor (not shown) and discharged to a condenser 10. The condenser 10 discharges the liquid refrigerant condensed within the condenser 10 to an expansion device 12, such as a poppet valve, float valve, or simple orifice.
supplies liquid refrigerant and evaporated refrigerant through conduit 13 to evaporator 14 of the refrigeration system. The liquid refrigerant in the evaporator 14 is evaporated and the liquid refrigerant in the evaporator 14 is
such as water flowing through heat transfer tubes (not shown) within the
Cooling the heat transfer fluid. The evaporated refrigerant exiting the evaporator 14 is discharged through a discharge line (not shown) to the suction side of the pre-air compressor where it begins the next refrigeration cycle.

Various non-condensable gases and other contaminants are
Usually mixed with refrigerant in the refrigeration system, condenser 1
It accumulates at 0. Purifying a refrigeration system without losing refrigerant requires separating noncondensable gases and other contaminants from the refrigerant. Purge chamber 15
is provided for this purpose. Condenser 1
Extract the gaseous mixture from 0 and transfer it to purge chamber 1
5, the purge chamber 15 is connected to the condenser 10 by a conduit 16. The gaseous mixture entering the purge chamber 15 typically includes a non-condensable gas,
It is a mixture of refrigerant vapor and water vapor.

The conduit 16 includes a strainer 17 for removing particulate matter entrained in the gaseous mixture coming from the condenser 10 and an orifice 18 for regulating the flow of steam between the condenser 10 and the purge chamber 15. have. Conduit 16 also includes a normally open valve 19 that allows purging under certain circumstances, such as when the refrigeration system is pressurized through valve 20 to leak test the refrigeration system. - Manually operated to isolate the system from the refrigeration system. Valve 20 is a purge valve.
It must be noted that it is closed during normal operation of the system and refrigeration system.

A condensing coil 21 is placed at the top of the purge chamber 15 to receive cold fluid used to condense the refrigerant vapor supplied to the purge chamber 15. This condensing coil 21 receives cold fluid from the condenser 10 of the refrigeration system. As shown in FIG. 1, an orifice 22 is provided in the inlet line to the condenser coil 21 to reduce the refrigerant pressure as liquid refrigerant is supplied from the condenser 10 to the condenser coil 21. Further, as shown in FIG. 1, a filter 23 is provided to remove particulate matter present in the refrigerant flowing from the condenser 10 to the condensing coil 21. Furthermore, it should be noted that in FIG. 1, the refrigerant exiting the condensing coil 21 is returned to the evaporator 14 through the refrigerant outlet line 24.

The cold fluid circulating through the condensing coil 21 in the purge chamber 15 lowers the temperature of the gaseous mixture of refrigerant, noncondensable gases, and other contaminants collected in the purge chamber 15, such as refrigerant vapor and water vapor. and other condensable substances. Low-density condensable substances such as water collect in a layer on the upper surface of the relatively clean liquid refrigerant condensed in the purge chamber 15.
Within the purge chamber 15 is a float valve 25 for controlling the level of liquid refrigerant in the purge chamber 15.
is provided. As the level of liquid in purge chamber 15 increases, float valve 15 automatically opens to discharge substantially clean liquid refrigerant from purge chamber 15 to evaporator 14 through line 36 . and,
When the level of liquid in purge chamber 15 falls below a predetermined level, float valve 25 closes.
An intermediate chamber 26 is provided to separate the condensed water from the condensed refrigerant. The liquid refrigerant exiting the intermediate chamber 26 is allowed to pass through the bottom of the purge chamber 15 where the float valve 25 is located. Since water is a liquid with a lower density than the refrigerant, it is trapped in the upper part of the intermediate chamber 26. A viewing window 27 is provided in the side wall of the intermediate chamber 26, making it possible to visually determine the level of water in the intermediate chamber 26. A manual valve 28 is also arranged on the side wall of the intermediate chamber 26 for draining the collected water.

Non-condensable gases such as air collect at the top of the purge chamber 15. As noncondensable gases gather,
The pressure in the purge chamber 15 increases and approaches the pressure in the condenser 10. A purge motor driven by an electric motor 29 is used to evacuate non-condensable gases.
A pump 50 is connected to the purge chamber 15 by a conduit 30. The pipe line 30 includes a check valve 31;
and a solenoid valve 32 for controlling the flow of noncondensable gas to a purge pump 50, having a solenoid coil 33.

Furthermore, as shown in FIG.
The system includes a normally closed purge operating switch 34 .
is a differential pressure switch that responds to the pressure difference between purge chamber 15 and condenser 10. The purge system also detects the temperature of the refrigerant within the evaporator 14;
It includes a first temperature sensor 1 that supplies a first electrical signal indicative of the detected temperature to electrical output leads 3, 4. Furthermore, the purge system includes a second temperature sensor 1 that detects the temperature of the refrigerant in the condenser 10 and provides a second electrical signal indicative of the detected temperature to the electrical output leads 5, 6. . Preferably, each temperature sensor 1, 2 is a temperature sensitive resistance device, such as a thermistor. However, as will be apparent to those skilled in the art to which the present invention pertains, each temperature sensor 1, 2 may be of various types suitable for detecting the temperature of the refrigerant and providing an electrical signal indicative of the detected temperature. It may be any temperature sensor.

Referring to FIG. 2, a control system for operating the purge system shown in FIG. 1 in accordance with the principles of the present invention is shown. An operating switch 44 is provided for switching the control system between a manual operating mode, an operating off mode, and an automatic operating mode. Power is 115V, 50Hz
or 60 Hz, which is supplied to the control system through electrical wiring 40, 41 connected to a power source such as an AC power source. Power is supplied from the power supply through a transformer 42 to a processor board 43, which is preferably a model sold by Intel Corporation, which has a business location in Santa Clara, California, USA. 8031, including microcomputers such as microcomputers.
The processor board 43 is connected to a system interface board 47 through an interconnect 46, such as a ribbon cable.
Power is also provided directly from electrical line 40 through electrical line 52 to system interface board 47 .

The system interface board 47
includes at least one switching device, preferably a model sold by CTS, Inc., with offices in Skyland, North Carolina, USA.
SC-140, tri-ax like tri-ax
It includes a switch 55. A triac switch 55 on the system interface board 47 is electrically connected to control the supply of power to the relay 48 from the electrical wiring 52. The triax switch 55 connects the triax switch 55 from a photocoupler circuit 57 on the system interface board 47.
The gate G is opened and closed in response to an electric signal supplied to the gate G of the gate G. The photocoupler circuit 57 includes a processor
It is controlled by control signals provided to the optocoupler circuit 57 from board 43 through interconnect 46. This photocoupler circuit 57 mainly consists of:
It is provided to isolate the processor board 43 from the 115V power supply while allowing the processor board 43 to control the triac switch 55.

The processor board 43 is directly connected through output leads 3, 4 to monitor the electrical signals obtained by the temperature sensor 1. The processor board 43 is also directly connected through output leads 5 and 6 to monitor the electrical signals obtained by the temperature sensor 2.
In this manner, processor board 43 monitors the temperature of the refrigerant in evaporator 14 and the temperature of the refrigerant in condenser 10.

As shown in FIG. 2, the purge operation switch 34 is connected to the system interface board 4.
7 in electrical series. The optocoupler circuit 56 on the system interface board 47 is at 115V when the switch 34 is closed.
is electrically connected to provide an output signal to the processor board 43 through the ribbon connector 46 when supplying the power supply voltage from the electrical line 40 to the system interface board 47 through the electrical line 53. Similar to photocoupler circuit 57, the primary purpose of this photocoupler circuit 56 is also to connect the 115V
The purpose is to isolate the processor board 43 from the power supply of the processor board 43. In this regard, circuits 56, 5 will be readily apparent to those skilled in the art to which the present invention pertains.
It should be noted that each of 7 may be an optically isolated triac triggering circuit or other similar suitable circuit.

Further, as shown in FIG. 2, the solenoid coil 33 of the solenoid valve 32 is electrically connected in parallel with the purge pump motor 29. Also,
As shown in FIG. 2, both purge pump motor 29 and solenoid coil 33 are connected to normally open relay contacts 49 that are controlled by the operation of relay 48. The normally open relay contact 49 and the operating switch 44 are electrically connected in parallel, as shown in FIG.
Further, as shown in FIG. 2, a solenoid switch 51 is electrically connected in series with the solenoid coil 33. This solenoid switch 51 is closed during normal automatic operation of the purge system. This solenoid switch 51 provides manual control of the solenoid coil 33 in certain circumstances, such as during initial startup of the refrigeration system and when servicing and testing the purge and/or refrigeration system. It is provided only to enable.

In operation, when the operating switch 44 is switched to the manual operating mode, power is supplied to the purge pump motor 29 and the purge pump 50
continuously moving independently of other elements of the control system. This mode of operation is only desirable in certain special situations, such as during initial start-up of the refrigeration system and when servicing or testing the purge and/or refrigeration system.

When operating switch 44 is switched to the operational off mode, power is sufficiently disconnected from the control system to render it inoperable. This mode of operation is also used during initial start-up of the refrigeration system, and when servicing and testing the purge and/or refrigeration system.
Desirable only in certain special circumstances.

When the operating switch 44 is switched to the automatic mode of operation, the control system automatically controls the operation of the purge system. This automatic operating mode is the normal operating mode when the refrigeration system is operating under normal conditions. In this automatic mode of operation, power is passed from the power supply through electrical wiring 40, 41 and transformer 42 to processor board 43.
and thereby processor board 4.
Activate 3. In addition, power is transferred from the power supply to the electrical wiring 5
2 to the system interface board 47. Furthermore, power is obtained through the electrical wiring 53 to the purge operation switch 34.

In the automatic operation mode, the purge operation switch 34 is normally closed when the refrigeration system is started. This is because the pressure differential necessary to change the position of this switch 34 does not exist in the refrigeration system. However, immediately after booting,
The pressure difference increases, causing the purge operation switch 34 to open. Therefore, immediately after startup, normally,
Power is not provided through electrical wiring 53 to optocoupler circuit 56 on system interface board 47. Thus, system interface board 47 to processor board 43
No output signal is provided to the processor board 43, and in response, the processor board 43 causes the relay 48 to become inactive and the associated relay contact 49 to open.
It operates to keep the triac switch 55 on the system interface board 47 open. Since relay contact 49 is open, solenoid coil 33 and purge pump motor 29 are also inactive;
thereby interfering with the operation of the purge system.

Further, when starting up the refrigeration system in the automatic operation mode, the processor board 43 processes electrical signals supplied to the processor board 43 from the temperature sensors 1 and 2 according to a preprogrammed procedure, and processes the electrical signals supplied to the processor board 43 from the temperature sensors 1 and 2 to The temperature difference between the refrigerant in 14 and the refrigerant in condenser 10 is determined. If this temperature difference
If the value is less than a preselected value, below which it is undesirable to operate the purge system for safety reasons, the processor board 43
generates a control signal. This control signal is then provided to the photocoupler circuit 57 on the system interface board 47 through the interconnect 46 and to the gate G of the triac switch 55 on the system interface board 47.
An electrical signal is provided to open switch 55, thereby deactivating relay 48 and opening relay contacts 49, preventing energization of solenoid coil 33 and purge pump motor 29. In this way, this purge system
Operation is inhibited when the temperature difference of the refrigerant between the evaporator 14 and the condenser 10 is less than a selected value below which it is undesirable for safety reasons to operate the purge system. .
Thus, in effect, the arrangement described above provides a purge safety switch function for the purge system.

However, when condenser 10 and evaporator 14 reach their normal operating temperature and pressure,
A sufficient refrigerant temperature difference exists between them, and the processor board 43 senses through temperature sensors 1 and 2 that the purge system is allowed to operate. Also, after a sufficient operating time interval, the non-condensable gas is purged enough to cause a decrease in the pressure differential between purge chamber 15 and condenser 10 sufficient to close purge operation switch 34. Room 1
We will gather at 5. When the purge operation switch 34 closes under these conditions, the processor board 43
generates a control signal that causes triac switch 55 on system interface board 47 to close.

In this way, relay 48 is energized and closes the associated relay contact 49. Power is thus supplied to the purge pump motor 29 and the solenoid coil 33 of the solenoid valve 32 so that the purge pump 50 discharges non-condensable gas from the purge chamber 15 to the atmosphere. Reduce pressure.

The purge chamber 1 is opened by the operation of the purge pump 50.
When the pressure at 5 drops to a level sufficient to open purge operation switch 34, processor board 43 generates a control signal to open triac switch 55 on system interface board 47. Thus, relay 48 is deenergized,
The associated relay contact 49 is opened, thereby stopping operation of the purge pump motor 29 and closing the solenoid valve 32. The foregoing sequence of operations is repeated each time sufficient noncondensable gas accumulates in purge chamber 15 to cause purge operation switch 34 to close.

During operation of the refrigeration system, the processor board 43 continuously monitors the temperature difference of the refrigerant between the condenser 10 and the evaporator 14 through temperature sensors 1 and 2, which temperature difference is determined by the selected temperature difference. Once the purge pump 50 has fallen below this level, the triax switch 55 is opened to prevent operation of the purge pump 50. This feature prevents the operation of the persi pump 50 during certain periods when operating the purge system is undesirable, such as when the refrigeration system is idle. This feature also eliminates the possibility of the purge system running continuously when the refrigeration system is operating at low head.

Of course, while the foregoing description has been made of one particular embodiment of the invention, various modifications and other embodiments of the invention will be readily apparent to those skilled in the art to which this invention pertains. Will. Thus, while the invention has been described with respect to particular embodiments, it is contemplated that various modifications may be made thereto without departing from the scope of the invention as herein described and claimed. It should be understood that and other embodiments may be made.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a refrigeration system having a purge system operated in accordance with the principles of the present invention. FIG. 2 is a schematic diagram of a control system for operating the purge system shown in FIG. 1 in accordance with the principles of the present invention. 1... First temperature sensor, 2... Second temperature sensor, 15... Purge chamber, 21... Condensing coil,
29...Electric motor, 32...Solenoid valve, 33...
Solenoid coil, 34... Purge operation switch, 43... Processor board, 47... System interface board, 48... Relay, 49... Relay contact, 50... Purge pump, 56, 57... Photocoupler circuit.

Claims (1)

[Scope of Claims] 1. A refrigeration system having an evaporator, a condenser, and a purge system for removing noncondensable gas from the refrigeration system, the temperature of the refrigerant in the evaporator of the refrigeration system being a first temperature sensor that detects and provides a first electrical signal indicative of the detected temperature; and a first temperature sensor that detects a temperature of a refrigerant in the condenser of the refrigeration system and provides a second electrical signal indicative of the detected temperature. a second temperature sensor; receiving the first electrical signal and the second electrical signal provided by the first temperature sensor and the second temperature sensor; an electrical signal and a second electrical signal are processed according to a preprogrammed procedure to determine a temperature difference between the refrigerant in the evaporator and the refrigerant in the condenser, the determined temperature difference being preselected; electrical control means for generating a control signal when the purge system is less than a specified value; and switch means connected to said control means to prevent operation of said purge system in response to generation of said control signal by said control means. A refrigeration system. 2. The refrigeration system of claim 1, wherein the first temperature sensor comprises a temperature sensitive resistance device located in the evaporator of the refrigeration system. 3. The refrigeration system of claim 1, wherein the second temperature sensor comprises a temperature sensitive resistance device located in the condenser of the refrigeration system. 4. The refrigeration system of claim 1, wherein said electrical control means comprises a microcomputer control system. 5. The switch means includes: a power supply means for supplying electric power to a motor for operating a purge pump in the purge system; and a power supply means disposed between the power supply means and the motor of the purge pump, and the switch means is arranged between the power supply means and the motor of the purge pump, and in response to generation of the control signal, interrupting the flow of power from the power source through the purge pump motor;
2. The refrigeration system of claim 1, further comprising an electronic switching device for interfering with operation of said purge system. 6. A refrigeration system operating method for operating a refrigeration system having an evaporator, a condenser, and a purge system for removing noncondensable gases from the refrigeration system, the method comprising: detecting and providing a first electrical signal indicative of the detected temperature; detecting the temperature of a refrigerant in a condenser of the refrigeration system and providing a second electrical signal indicative of the detected temperature; a comparison step of comparing the first electrical signal and the second electrical signal to determine a temperature difference between the refrigerant in the evaporator and the refrigerant in the condenser; disabling operation of the purge system when the comparison step determines that the temperature difference between the purge system and the refrigerant is less than a preselected value. 7. Interfering with operation of the purge system includes: comparing the first electrical signal and the second electrical signal to determine a temperature difference between the refrigerant in the evaporator and the refrigerant in the condenser; , preventing the flow of operating power from a power source to the purge system when determined by the comparing step to be less than the preselected value;
A method of operating a refrigeration system according to claim 6.